(1) Field of the Invention
The present invention relates to a recording member for recording informations. More particularly, the present invention relates to a recording member having a film which is deformed or removed under irradiation with energy beams to form a concave or hole portion.
(2) Description of the Prior Art
In the field of optical video discs or digital optical discs, development of a recording member in which a large signal-to-noise ratio and a small error rate can be obtained even if an image information of a very high density is recorded has been tried. For example, a film of bismuth (Bi) or tellurium (Te) or a chalcogenide glass film of the arsenic-tellurium type is known as a recording layer to be formed on a disc substrate. In case of a optical video disc, a reproduced signal having a highest quality can be obtained when a film of the As-Te type is used, but in case of a digital optical disc, good characteristics can also be obtained even if a film of Bi or Te is used. Such film can absorb laser beams more easily than films of metals such as Al, and it has a low melting point (softening point), a low boiling point and a low heat conductivity, and therefore, it has a very high recording sensitivity.
These recording films are disclosed in, for example, Japanese Pat. No. 40479/1971 and Japanese Laid-Open Patent Applications Nos. 87304/1975, 42489/1975 and 51733/1975. One of us has already discloses a recording film of the As-Te-Se type in the specification of U.S. Pat. No. 4,238,803.
Since As, Te and Bi are oxidized if they are allowed to stand in air for a long time, they cannot be used stably over a long period. Furthermore, vacuum deposition of As alone cannot be performed stably, and it has been found that when an As-Te type material is used for vacuum deposition, the composition of the vacuum deposition product is changed with the lapse of time and good reproducibility can hardly be obtained at vacuum deposition.